I have a 2005 Mitsubishi mini-split that has been working OK but blew the fusible plug (on the low side just before compressor) this winter while it was in heating mode. Now I'm wondering what to do.
I discovered the problem by blowing nitrogen into the service port (all the R-22 is long gone) and feel it come out straight the fusible plug. The service manual says zip.
I gather this can be due to a blockage or to a refrigerant over-charge. I will see whether I can access the strainer. I'm not sure what else to do (or where to get a replacement plug given the unit's age).
The last time the unit was serviced is in 2008 where a service tech tightened the flare nuts due to leakage and added refrigerant eyeballing it, so it could well have been overcharged. It was used more heavily this winter in heating mode than previous years, but it's still suspect to me that it would fail after this much time.
Any thoughts/advice would be appreciated!
NB: I know that getting a new R-22 charge is going to cost "a lot" but I also know that it's less than a new unit.
Update: photo of blown fusible plug laying on top of the piece of tubing into which it was screwed, which is covered by the black plastic tape to avoid too much more contamination. (Oops, looks like SX is having trouble with images?)